29-08-2011, 02:44 PM
cruise control devices.ppt (Size: 2.3 MB / Downloads: 152)
Cruise control device first appeared in 1970 in USA
Assisting drivers in longitudinal vehicle control
Avoid collisions
Adaptive cruise control (ACC) developed as new generation
Cruise control is a system that automatically controls the speed of a motor vehicle.
Also known as speed control or auto cruise.
Adjusting the throttle position to maintain a speed set by the driver.
Uses the principle of radar to determine the distance between two consecutive moving vehicle.
The electromagnetic rays from radar system are sensed by sensors.
Advanced innovation in automotive technology.
Luxury vehicles offer ACC. Mercedes Benz first offer ACC.
Distance sensor is used.
The set distance (timed in seconds) is the desired distance between the ACC vehicle and the forward vehicle.
The set speed is the desired maximum speed to be regulated by the ACC system on an open road. If no forward vehicle is detected, the set speed is regulated.
PRINCIPLES OF ACC
Works by detecting the distance and speed of the vehicle using lidar or radar system
Speed is measured by Doppler effect
Second generation of ACC is stop and go cruise control (SACC)
ACC is control is a radar-based system that can monitor the vehicle in from (upto 600 feet) and adjust the speed of the vehicle to keep it at a pre-set distance behind the lead vehicle, even in most fog and rain conditions.
The system measures distance as a function of speed and can monitor the traffic
When the danger of a collision is detected, it provides a red warning light that flashes on the windshield.
The system provides an audible alert when it senses a reduction in traffic speed in vehicles ahead.
SENSOR OPTION
LIDAR
RADAR
FUSION SENSORS
LIDAR
LIDAR is Light Detection And Ranging.
A laser diode was used to generate the light signal.
Beat frequency difference between a Frequency Modulated Continuous light Wave and its reflection is used as the control signal.
RADAR
RADAR is Radio Detection And Ranging
It is operated by radiating energy into space and detecting the echo signal reflected from target
The currently used ‘Pulse Doppler RADAR’ uses the principle of ‘Doppler effect’ in determining the velocity of the target.
PULSE DOPPLER RADAR
PULSE DOPPLER RADAR
Wave oscillator produces the signal to be transmitted
Duplexer is a switching device
Doppler filter removes the noise
RADAR ANTENNA SCHEMES
Mechanically steered antenna
Electronically steered antenna
MECHANICALLY STEERED ANTENNA
ELECTRONICALLY STEERED ANTENNA
Phased array is a directive antenna made up of a number of individual antenna or radiating element
Radiation pattern is determined by the amplitude and phase of the current at each of its element
FUSION SENSOR
While RADAR target is the car’s rear spoiler the stereo camera is constantly captures all objects in its field of view.
It includes millimeter wave radar linked to a 640x480 pixel stereo camera
Car with fusion sensor arrangement
Sensing and controlling process
MILLIMETER WAVE RADAR
Millimeter-wave radar is a method used for detecting the position and velocity of a distant object.
Every 60 milliseconds, the sensor sends out a trio of overlapping beams of electromagnetic radiations
Range is calculated using the formula
C=2*R/T
STEREO CAMERA
The camera’s function is the same, as that of the radar, detection of cars and other objects in the roadway. Camera view reaches to a distance of 60 meters ahead of the vehicle. The stereo camera is situated by the rear view mirror.
The image-processing unit processes the images from the stereo camera and the data is then fed into the fusion processor
The function of fusion processor is termed as Data Fusion. Data fusion is a collection of techniques for combining the measurements from more than one sensor to provide a more unified result.
ADVANTAGES OF ACC
The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics.
A highly responsive traffic system adjusts itself to avoid accidents.
Fuel efficiency of the vehicle is increased
A cheap version is not yet realized.
A high market penetration is required if a society of intelligent vehicles is to be formed.
Encourages the driver to become careless.
The ACC systems not respond directly to the traffic signals.
FUTURE ASPECTS
Co-Cooperative Adaptive cruise control or CACC is already being tested in California .
ACC respond to the distance and speed of the car ahead ,CACC communicate with two or more cars and work together to avoid collision.
Communication is quicker, reliable and responsive.
CONCLUSION
The accidents caused by automobiles are goes on increasing.
The safety measures starting from air bags and seat belts have now reached to ACC and CACC systems.
By the invention of 360° sensors, car accidents may be as rare as plane accidents.